Iowa Republican Sen. Chuck Grassley has started an investigation into whether Hillary Clinton acted to prevent a Bangladeshi probe into a Clinton Foundation donor, The Daily Caller reports.

Grassley, the chairman of the Judiciary Committee, sent a letter to the State Department requesting information regarding possible interference into a corruption investigation into Muhammad Yunus, a Bangladeshi banker and economist who is also a close friend of the Clintons.

In May, The Daily Caller reported that during her time at the State Department, Clinton had put pressure on Bangladesh to stop a probe into Yunus and Grameen Bank. The son of Bangladesh Prime Minister Sheikh Hasina even told The Daily Caller he had been threatened with an IRS audit if the investigation was not dropped.

“As I wrote in my August 2016 letter to Department of Justice, federal law requires that executive branch employees be disqualified from matters that have a direct and predictable effect on the employee’s own financial interests or the financial interests of those persons or organizations with which the employee is affiliated, such as those of a spouse, unless the employee first obtains an individual waiver or a regulatory exemption applies,” Grassley said in a letter to Secretary of State Rex Tillerson.

“Once again, Secretary Clinton’s actions have raised reasonable suspicions that she violated these rules and undermined the public’s confidence in the integrity of the State Department.”

“If the Secretary of State used her position to intervene in an independent investigation by a sovereign government simply because of a personal and financial relationship stemming from the Clinton Foundation rather than the legitimate foreign policy interests of the United States, then that would be unacceptable,” he added.

“Co-mingling her official position as Secretary of State with her family foundation would be similarly inappropriate. It is vital to determine whether the State Department had any role in the threat of an IRS audit against the son of the Prime Minister in retaliation for this investigation.”

If Grassley continues his look into the Grameen Bank affair, it would be the first major post-election congressional inquiry into either the Democrat presidential nominee or the Clinton Foundation.

While the Trump administration and the Republicans have not had much stomach for an investigation, this could actually be pretty big — and very bad news for Clinton. It could mean she’s spending less times on hikes in the woods and a lot more time in a lawyer’s office.